Substrate with conductor micropattern

ABSTRACT

The present disclosure provides an article having a conductor micropattern disposed on a major surface of a substrate. The conductor micropattern includes a plurality of curved traces defining a plurality of cells not lying on a repeating array. The conductor micropattern may have a uniform distribution of trace orientation. The conductor micropattern may be a tri-layer material including in sequence a semi-reflective metal, a transparent layer, and a reflective layer disposed on the transparent layer. The articles are useful in devices such as displays, in particular, touch screen displays useful for mobile hand held devices, tablets and computers. They also find use in antennas and for EMI shields.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.15/491,430, filed Apr. 19, 2017, which is a continuation of U.S.application Ser. No. 15/070,653, filed Mar. 15, 2016 and issued as U.S.Pat. No. 9,661,746, which is a continuation of U.S. application Ser. No.13/979,722, filed Jul. 15, 2013 and issued as U.S. Pat. No. 9,320,136,which is a national stage filing under 35 U.S.C. § 371 ofPCT/US2012/023480, filed Feb. 1, 2012, which claims the benefit of U.S.Provisional Patent Application No. 61/438,800, filed Feb. 2, 2011, thedisclosure of which is incorporated by reference herein in its entirety.

BACKGROUND

The use of metal-based conductor mesh for application where lighttransmission and electrical conductance are needed is known in the art.Examples of such applications include shielding for electromagneticinterference for displays. In the industry, a mesh is typicallyunderstood to mean a pattern geometry having connected traces that areseparated by open area to form cells.

It has been observed in the current work that some mesh designs, whenintegrated into a display and viewed under reflected, collimated light(such as in direct sunlight), may produce undesirable visual effects.Illustrative undesirable visual effects include, e.g., a starburstpattern for reflected light and bands of colored reflected light(similar to a rainbow) caused by light interference, each beingobservable when a mesh containing linear traces and a repeating cellgeometry is disposed an unmodified substrate, such as a plastic film orglass. Illustrative examples of meshes with linear traces include thosehaving hexagonal and square cells. Sparkle, which is an undesirablevisual appearance of points of reflected light, can also appear forlinear traced-based conductor meshes.

Some skilled in the art have attempted to reduce the visual appearanceof overlaid mesh micropatterns by using wavy traces in producing adisplay, such as a touch screen display. See, e.g., PCT InternationalPublication No. WO 2010/099132 A2 describing a articles such asantennas, electromagnetic interference shields and touch screen sensorshaving a light transparent substrate and two conductive meshes, eachhaving linear traces, where the first mesh overlays a second mesh in acertain configuration so as to minimize the traces' visibility.

Others have attempted to use ambient light reducing members such as anoptical interference member. See PCT International Publication No. WO2003/105248 disclosing an optical interference member including asemi-absorbing member layer for reflecting a portion of incident ambientlight, a substantially transparent layer for phase shifting anotherportion of ambient light and a reflective layer for reflecting the phaseshifted ambient light such that the two reflected portions of light areout-of-phase and thereby destructively interfere.

SUMMARY

There is a desire to improve the visual appearance of the metal-basedconductor meshes, in terms of reducing their visibility, when the meshis integrated into a display and viewed under reflected, collimatedlight, such as in direct sunlight.

The present disclosure provides articles using modified substrates orconductive optical interference layer in combination with designs ofconductor micropatterns. When integrated into a display or device, thecombination reduces the undesirable visual effects, such as starburst,sparkle, halo and rainbow, when the display or device is viewed underlight, including but not limited to collimated or nearly collimatedlight, such as sunlight.

In one aspect, the present disclosure pertains to an article comprising(a) a substrate having opposing first and second surfaces; and (b) aconductor micropattern disposed on the first surface of the substrate,the conductor micropattern comprising a plurality of traces defining aplurality of cells, wherein the conductor micropattern has an open areafraction greater than 80% and a uniform distribution of traceorientation; and each of the traces has a trace width from 0.5 to 10micrometer, and wherein the conductor micropattern comprises a tri-layermaterial comprising, in sequence, a semi-reflective metal, a transparentlayer, and a reflective layer disposed on the transparent layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be further described with reference to the followingdrawings, wherein:

FIG. 1 is a top plan view of a schematic of a regular hexagonalmicropattern;

FIG. 2 is a top plan view of a schematic of a portion of a polygonalmicropattern, referred to herein as a pseudorandom hexagonalmicropattern;

FIG. 3 is a top plan view of a schematic of a first illustrativenon-linear micropattern design, based on a regular hexagon, and referredto herein as a partially curved hexagon micropattern;

FIG. 3a is an exploded view of a few cells of the micropattern of FIG.3;

FIG. 4 is a top plan view of a schematic of a second illustrativenon-linear micropattern design, based on a regular hexagon, and referredto herein as a fully curved hexagon micropattern;

FIG. 4a is an exploded view of a few cells of the micropattern of FIG.4;

FIG. 5 is a top plan view of a third illustrative non-linearmicropattern, a pseudorandom curved design;

FIG. 6 shows a cell in a micropattern illustrating a measurement methodto determine an orientation to a trace;

FIG. 7 shows a histogram of the orientation of normal to the tracesegments for the micropattern of FIG. 1;

FIG. 8 shows a histogram of the orientation of normal to the tracesegments for the pseudorandom hexagonal micropattern, a portion of whichis illustrated in FIG. 2;

FIG. 9 shows a histogram of the orientation of normal to the tracesegments for the partially curved hexagonal micropattern, a portion ofwhich is shown in FIG. 3;

FIG. 10 shows a histogram of the angular distribution of the traceorientations for the fully curved hexagonal micropattern, a portion ofwhich is shown in FIG. 4;

FIGS. 11, 11 a and 11 b show various portions of a first micropatternedsubstrate useful for integration into a device, such as a display;

FIGS. 12, 12 a and 12 b show various portions of a second micropatternedsubstrate useful for integration into a device, such as a display;

FIG. 13 shows the overlay of the first and second micropatternedsubstrate that can be integrated into a device; and

FIG. 14 is a top plan view of a third illustrative non-linearmicropattern, referred to herein as a fully curved square micropattern.

These figures are not drawn to scale and are intended for illustrativepurposes.

DETAILED DESCRIPTION

Unless otherwise indicated, all numbers expressing feature sizes,amounts and physical properties used in the specification and claims areto be understood as being modified in all instances by the term “about.”Accordingly, unless indicated to the contrary, the numerical parametersset forth in the foregoing specification and attached claims areapproximations that can vary depending upon the desired propertiessought to be obtained by those skilled in the art using the teachingsdisclosed herein.

The recitation of numerical ranges by endpoints includes all numberswithin that range (e.g., 1 to 5 includes, 1, 1.5, 2, 2.75, 3, 3.80, 4and 5) and any range within that range.

As used herein “micropattern” refers to an arrangement of dots, traces,filled shapes, or a combination thereof, each having a dimension (e.g.trace width) of no greater than 1 mm. In preferred embodiments, themicropattern is a mesh formed by a plurality of traces defining aplurality of cells, each trace having a width of at least 0.5 micronsand typically no greater than 20 microns. The dimension of themicropattern features can vary depending on the micropattern selection.In some favored embodiments, the micropattern feature dimension (e.g.trace width) is less than 10, 9, 8, 7, 6, or 5 micrometers (e.g. 1 to 3micrometers). Linear and non-linear traces are useful in the presentdisclosure.

As used herein, “visible light transparent” refers to the level oftransmission of the unpatterned substrate or of the article comprisingthe micropatterned substrate being at least 60 percent transmissive toat least one polarization state of visible light, where the percenttransmission is normalized to the intensity of the incident, optionallypolarized light. It is within the meaning of visible light transparentfor an article that transmits at least 60 percent of incident light toinclude microscopic features (e.g., dots, squares, or traces withminimum dimension, e.g. width, between 0.5 and 10 micrometers, between0.5 and 5 micrometers, or between 1 and 5 micrometers) that block lightlocally to less than 60 percent transmission (e.g., 0 percent); however,in such cases, for an approximately equiaxed area including themicroscopic feature and measuring 1000 times the minimum dimension ofthe microscopic feature in width, the average transmittance is greaterthan 60 percent. The term “visible” in connection with “visible lighttransparent” is modifying the term “light,” so as to specify thewavelength range of light for which the substrate or micropatternedarticle is transparent.

As used herein, “open area fraction” (or open area or percentage of openarea) of a conductor micropattern, or region of a conductormicropattern, is the proportion of the micropattern area or region areathat is not shadowed by the conductor. The open area is equal to oneminus the area fraction that is shadowed by the conductor micropattern,and may be expressed conveniently, and interchangeably, as a decimal ora percentage. Area fraction that is shadowed by conductor micropatternis used interchangeably with the density of lines for a conductormicropattern. Illustrative open area fraction values useful in thepresent disclosure are those greater than 50%, greater than 75%, greaterthan 80%, greater than 90%, greater than 95%, greater than 96%, greaterthan 97%, greater than 98%, greater than 99%, 99.25 to 99.75%, 99.8%,99.85%, 99.9% and even 99.95. In some embodiments, the open area of aregion of the conductor micropattern (e.g., a visible light transparentconductive region) is between 80% and 99.5%, in other embodimentsbetween 90% and 99.5%, in other embodiments between 95% and 99%, inother embodiments between 96% and 99.5%, in other embodiments between97% and 98%, and in other embodiments up to 99.95%.

As used herein, “trace” refers to the geometric element given by theintersection of two planes or by the intersection of a plane and anon-planar surface. The geometric element given by the intersection oftwo planes is described herein as linear (or, as a linear trace). Thegeometric element given by the intersection of a plane and a non-planarsurface is described herein as non-linear (or, as a non-linear trace). Alinear trace has zero curvature, or stated differently it has infiniteradius of curvature. A non-linear trace has non-zero curvature, orstated differently it has a finite radius of curvature. Curvature orradius of curvature can be determined for any point along a trace, as isknown in analytic geometry. Also, a normal can be constructed at a pointthat lies on a linear or non-linear trace, as is also known in analyticgeometry.

As used herein, “antireflective” refers to the behavior of a surface orcoating that reduces Fresnel light reflection at the interface between amaterial and a surrounding medium to which the material is exposed, andenhances light transmission through the interface. In the absence of anantireflective surface or coating, Fresnel reflection is governed by thedifference between refractive indices of the material and thesurrounding medium, as is known in the art.

Micropattern Designs

A number of different geometries or designs can be used for conductormicropatterns useful for present disclosure. The classes of meshmicropattern design include: (A) those with repeating cell geometry, (B)those with non-repeating cell geometry, (C) those with cells havingcentroids that do not lie on a repeating array, (D) those that havecells where the traces have a uniform distribution of trace orientation.These classes are not mutually exclusive. Within each of these classes,the traces can be linear or non-linear (i.e., having some finite radiusof curvature). The mesh micropatterns described below are not limitedwith respect to the width of traces or the sizes of cells. In someembodiments, the traces have a width in the range of 0.1 to 20micrometers, in some embodiments in the range of 0.5 to 10 micrometers,in some embodiments in the range of 0.5 to 5 micrometers, in someembodiments in the range of 0.5 to 4 micrometers, in some embodiments inthe range of 0.5 to 3 micrometers, in some embodiments in the range of0.5 to 2 micrometers, in some embodiments from 1 to 3 micrometers, insome embodiments in the range of 0.1 to 0.5 micrometers. In someembodiments, the open area of a region of the mesh conductormicropattern (e.g., a visible light transparent conductive region) isbetween 80% and 99.5%, in other embodiments between 90% and 99.5%, inother embodiments between 95% and 99%, in other embodiments between 96%and 99.5%, in other embodiments between 97% and 98%, and in otherembodiments up to 99.95%.

(A) Micropatterns with Repeating Cells

A characteristic of repeating cell geometries is that the cells lie on arepeating array. For cells to lie on a repeating array, what meant isthat the centroids of the cells lie no greater than a short distanceaway from positions that define the array (under the limit that there beonly one array position per cell). This description of the positionalrelationship of cells focuses on the open areas (or openings) of themesh cells, not on the traces or the trace junctions (vertices) of themesh. In some instances where cells lie on a repeating array, thecentroids of the cells lie precisely on the array of points (i.e.,positions). By arrays, what is meant is an arrangement of positions intwo-dimensions (i.e., in the plane of the micropattern) characterized bydiscrete translational symmetry for a unit cell comprising no more thanpositions. The translational symmetry of the array is defined in termsof one or more basis vectors that define the minimum translation withinthe plane of the micropattern over which the array is invariant. In thiscontext, arrays can include square arrays (or square lattices),rectangular arrays (or rectangular lattices), or triangular arrays (ortriangular lattices), for example. By a short distance, as this termrelates to the allowance for centroids of a mesh comprising cells thatare described herein to lie on a repeating array to be displaced fromthe precise positions of the array, what is meant is a distance lessthan 50% of the value given by taking the length of the shortest arraybasis vector that can be constructed in the orientation of thedisplacement and dividing that length by the number of array positionsin the unit cell that is associated with that basis vector. In someembodiments where the cells lie on a repeating array, the distance bywhich the centroids are displaced from the positions of the array isless than 25% of the value given by taking the length of the shortestarray basis vector that can be constructed in the orientation of thedisplacement and dividing that length by the number of array positionsin the unit cell that is associated with that basis vector. Illustrativeexamples of these types of micropatterns are shown in FIGS. 1, 3, 4 and14.

Turning now to the figures, FIG. 1 shows a top plan view of anillustrative geometry of a regular hexagonal conductor micropattern 10that is formed by a plurality of linear traces 12. Six traces, 12 athrough 12 f, form a cell 14 having an open area. As shown, each traceis of substantially equal length and each of the six internal angles isof substantially 120°. The centroids of the mesh cells lie on atriangular lattice (or array). The distance from the centerline of atrace defining one edge of the hexagonal cell to the centerline of the(parallel) trace defining the opposite edge of the hexagonal cell is,for example, 200 micrometers.

FIG. 3 shows a top plan view of an illustrative geometry of a non-lineardesign, i.e., a partially curved hexagonal conductor micropattern 30formed by a plurality of curved traces 32 defining a plurality of openarea cells 34. In one method, this micropattern design can be generatedstarting from the regular hexagonal micropattern design shown in FIG. 1and displacing the midpoint of each trace by some distance, e.g., by 10micrometers, and allowing the trace to bow. FIG. 3a shows a magnifiedcell 34′ with six traces, 32 a through 32 f shown. One characteristic ofthe micropattern 30 is that tangents 36 a and 36 c for traces 32 a and32 c respectively are generally not parallel to one another. Similarlyto the mesh micropattern of FIG. 1, the centroids of the mesh cells ofFIG. 3 lie on a triangular lattice of points (i.e., array of points).

FIG. 4 shows a top plan view of an illustrative geometry of anothernon-linear design, a fully curved hexagonal conductor micropattern 40formed by a plurality of curved traces 42 defining a plurality of cells44. In one method, this micropattern design can be generated bydecreasing the radius of curvature of the traces shown in FIG. 3 by,e.g., further displacing the midpoints of each trace. FIG. 4a shows amagnified cell 44′ with six traces, 42 a through 42 f. Onecharacteristic of the micropattern 40 is that tangents 46 a and 46 c fortraces 42 a and 42 c respectively are generally parallel to one another.Similarly to the mesh micropattern of FIG. 1, the centroids of the meshcells of FIG. 4 lie on a triangular lattice of points (i.e., array ofpoints).

FIG. 14 shows another exemplary non-linear micropattern design 240 thatcan be generated starting from a square and displacing the midpoint ofeach side of the square by some distance, and allowing the trace to bow.Four traces, 242 a to 242 d are shown defining open area cells 244. Thecentroids of the mesh cells of FIG. 14 lie on a square lattice (i.e.,array of points).

(B) Micropatterns with Non-Repeating Cells

For mesh micropatterns having non-repeating cell geometry, the cells maylie on a repeating array (e.g., a rectangular array, a square array, ora triangular array) or they may not. In this cell geometry, the cellsare not of the same size and the same shape. An illustrative example ofthis type of cell geometry is shown in FIG. 2.

FIG. 2 shows a top plan view of an illustrative geometry of apseudorandom hexagonal conductor micropattern 20 formed by plurality oflinear traces 22 defining a plurality of cells 24. In one method, thismicropattern design can be generated by starting from the regularhexagonal pattern design shown in FIG. 1 and displacing the vertices ina randomized direction and by a randomized distance less than the edgelength of the original hexagonal cell, and maintaining linear traces.One characteristic of the micropattern 20, when generated by displacingvertices by a distance less than the edge length of the originalhexagonal cell (e.g., by a distance less than half of the edge length),is that the centroids of the cells lie within a short distance from thepoints of an array defined by the original centroid locations of thecells of the mesh of FIG. 1. More specifically the centroids of thecells of the mesh of FIG. 2 lie within a distance equal to 50% of theminimum separation between array positions defined by the centroids ofthe original mesh of FIG. 1 (i.e., 50% of the length of a basis vectorin the direction of the displacement, for triangular lattice defined bythe hexagonal mesh cell centroids). This result is due to the fact thatthe centroid of each original mesh cell opening of FIG. 1 has not beendisplaced substantially by the procedure of slightly moving thevertices. In this case, the cells are referred to herein as lying on anarray. In some embodiments disclosed later herein, the locations ofcentroids (not just the locations of vertices) are also specified to berandomized.

(C) Micropatterns with Cells not on an Array

As defined above, if the cells of a mesh micropattern are arranged intwo dimensions in such a way that the centroids of the cells lie nogreater than a short distance from positions that define an array, thenthe mesh cells are regarded herein to lie on a repeating array (or on anarray). In some instances where cells lie on a repeating array, thecentroids of the cells lie precisely on the array of points. Acharacteristic of a micropattern having cells not on a repeating array(i.e., not lying on a repeating array), as the term is used herein, isthat the centroids of the mesh cells (i.e., centroids of the cellopenings) are arranged in such a way that no array of positions can beconstructed using a unit cell comprising four or fewer positions, suchthat all of the centroids of the mesh lie within a distance less than50% of the value given by taking the length of the shortest array basisvector that can be constructed in the orientation of the displacementand dividing by the number of array positions in the unit cell that isassociated with that basis vector (under the additional limitation thatthere be only one array position per mesh cell). For this meshmicropattern, the cells are generally not of the same size and shape. Ofthe three micropatterns discussed thus far (A, B, and C), the C-typemicropattern has a higher degree of disorder. An illustrative example ofthis type of cell geometry is shown in FIG. 5.

FIG. 5 shows a top plan view of a portion of yet another non-lineardesign, a pseudorandom curved conductor micropattern 50 formed by aplurality of traces 52 defining a plurality of open area cells 54. Thisgeometry includes cells defined by curved conductive traces, each havingan exemplary width of 2 micrometers. The cells of a conductormicropattern with the pseudorandom curved design may have a varyingnumber of edges or traces that define the cells, e.g., from four toeight edges. The sizes of the cells vary from an area of 10,000 squaremicrometers to an area of 70,000 square micrometers. For reference, thearea of the regular hexagonal micropattern of FIG. 1 is 35,000 squaremicrometers. The positions of the cells, e.g., as defined by thecentroid of each cell, do not lie on a regularly spaced array.

D. Micropatterns with Uniform Distribution of Trace Orientation

A characteristic of this type of micropattern is that it is not limitedin terms of a cell geometry or in terms of the position of the centroidsof cells. To better describe this type of micropattern geometry, theconcept of angular distribution of trace orientation is used.

Angular Distribution of Trace Orientations

Each trace design can be characterized by an angular distribution oftrace orientations, as further described herein. The angulardistribution of trace orientations for the pseudorandom curved designsherein, as measureable according to a procedure described herein andover an area of 1 centimeter by 1 centimeter, is substantially uniform.For example, in some embodiments, with respect to the uniformity of thedistribution, no reference orientation can be established within theplane of the micropattern for which there are no normals to tracesegments in the micropattern that exist within plus or minus 10 degreesof that reference orientation. In some cases, no reference orientationcan be established within the plane of the micropattern for which thereare no normals to trace segments in the micropattern that exist withinplus or minus 5 degrees of that reference orientation. In some cases, noreference orientation can be established within the plane of themicropattern for which there are no normals to trace segments in themicropattern that exist within plus or minus 2 degrees of that referenceorientation. Further with respect to the uniformity of the distribution,over, e.g., 1 centimeter by 1 centimeter area, there are no two 20°ranges of orientation in the plane of the micropattern for which theintegrated density of the normals to the trace segments in the tworanges is different by more than 50% of the smaller of the twointegrated density values. In some cases, over, e.g., 1 centimeter by 1centimeter area, there are no two 20° ranges of orientation in the planeof the micropattern for which the integrated density of the normals tothe trace segments in the two ranges is different by more than 25% ofthe smaller of the two integrated density values. In some cases, over,e.g., 1 centimeter by 1 centimeter area, there are no two 20° ranges oforientation in the plane of the micropattern for which the integrateddensity of the normals to the trace segments in the two ranges isdifferent by more than 10% of the smaller of the two integrated densityvalues. In some cases, over, e.g., 1 centimeter by 1 centimeter area,there are no two 10° ranges of orientation in the plane of themicropattern for which the integrated density of the normals to thetrace segments in the two ranges is different by more than 10% of thesmaller of the two integrated density values. In some cases, over, e.g.,1 centimeter by 1 centimeter area, there are no 5° ranges of orientationin the plane of the micropattern for which the integrated density of thenormals to the trace segments in the two ranges is different by morethan 10% of the smaller of the two integrated density values.

The micropatterns of the present disclosure provide for the simultaneousminimization of a large number of potentially undesirable visualfeatures with have been observed for other micropatterns, especiallywhen combined with an information display (e.g., on a mobile phone,smart phone, tablet computer, laptop computer, desktop computer monitor,reading device, automotive display, or retail display). Thesepotentially undesirable visual features include starburst, rainbow, andsparkle, as already described. The potentially undesirable features thatare mitigated by the micropattern designs also include moiréinterference with the pixel pattern of the display. The potentiallyundesirable features that are mitigated by the micropattern designs alsoinclude substantial blockage (e.g., 25%, 50%, or even 75%) of theviewability of individual pixels of the display (obscuring theinformation, but not necessarily leading to a moiré pattern). It iswithin the scope of this disclosure for the micropattern to be tilted(e.g., rotated or biased) with respect to a display, in order tooptimize the mitigation of one or more of the potentially undesirablevisual features. Tilting of the micropattern can be especially usefulfor minimizing moiré interference with a pixilated display. In somecases, a four-sided cell geometry, distributed on a square array ofpositions (e.g., fully curved square cell geometry) is convenient forminimization of moiré interference though tilting.

The orientations of the population of traces useful in the presentdisclosure can be quantified as a distribution that describes therelative concentration, presence, or abundance of trace segments ofdifferent orientations within the micropattern. This distribution can beused to describe the orientations of the population of traces inmicropatterns that comprise linear traces or non-linear traces. Also, itcan be used to describe the orientations of the population of traces inmicropatterns that comprise repeating geometries (e.g., as in the caseof a square or hexagonal micropattern) or in micropatterns that comprisenon-repeating geometries (e.g., as in the case of pseudorandommicropattern designs comprising linear (as in FIG. 2) or non-linear (asin FIG. 5) traces. The descriptor is the integrated micropattern tracelength per unit area of micropattern, as a function of the orientationof a normal to the trace. Stated in another way, the descriptor can beexpressed as the frequency distribution of orientations for tracesegments (or the distribution of orientations of normals to the tracesegments) that form a conductor micropattern. By “integrated,” what ismeant is the summation of total trace width for traces within a definedarea that have the specified orientation.

In order to collect the above described frequency characteristics fororientations within conductor micropatterns having non-linear traces,the following procedure can be used. The procedure includes a series ofmanual drawing and measurement steps for a magnified print of themicropattern design on, for example, 11 inch by 17 inch paper. Thecharacterization procedure include the steps of (a) printing a magnifiedrendering of the micropattern on paper, (b) partitioning the traces ofthe micropattern into at least 200 segments of approximately equal pathlength, (c) manually drawing a normal to each segment, (d) establishingan orientation frame of reference by establishing a 0° direction, andthen (e) measuring the orientation of every normal with respect to the0° direction (e.g., using a protractor). The traces, and thus thenormals to the traces, can be specified using 180° of angular range forthe following reason. A trace that runs straight up and down can bearbitrarily described to be oriented up or down. A trace or its normalthat is oriented upward is no different from a trace or its normal thatis oriented downward. Thus, one cannot generate a trace that is orientedupward in any way different from a trace that is oriented downward(i.e., there is no meaning to a suggestion that the upward trace isdifferent from the downward trace). Thus, the full range of possibletrace segment orientations requires only 180° of angular range.

FIG. 6 shows a diagram of one full cell of the embodiment of FIG. 4where angle of a normal to a trace orientation is being measured attrace segment P₁. For purposes of simplicity, only one of the 200segments is shown. A normal line N to the trace segment P₁ is drawn asshown in the figure. A tangent line T is drawn intersecting both tracesegment P₁ and normal line N. A reference zero degree line is drawn asshown by a dashed arrow. An angle theta (θ) can then be measured todetermine the angle between the reference line and the normal line. Thismeasurement is then repeated multiple times for segments similar to P₁along each of the six traces. An arbitrary, but sufficiently largenumber of segments (in this case, 200 segments for statisticallysignificant measurement) can be drawn for the cell. An approximatelyequal number of segments is drawn for each of the six traces.

The so-measured distribution of the orientation of the normal to a tracesegment can be rendered by plotting a histogram of the orientationmeasurements. It should be noted that the distribution of theorientation of the normal to a trace segment provides a directcorrelation to the distribution of the orientation of the trace segmentitself. For micropatterns herein, the procedure was carried out for thetraces making up at least one complete cell of the micropattern. Formicropatterns having a single cell shape and size, replicated in twodirections in order to yield a two-dimensional micropattern,characterization of the traces that make up a single cell is adequate todetermine the distribution of trace orientations for the two dimensionalmicropattern over larger areas (for example over areas covering 10, 100,or even 1000 cells). For example, characterization of the traces thatmake up a single regular hexagonal cell measuring 200 micrometers indiameter is adequate to determine the distribution of trace orientationsfor a regular hexagonal micropattern of such cells measuring 1millimeter by 1 millimeter, 1 centimeter by 1 centimeter, or even 1meter by 1 meter. For micropatterns having multiple cell shapes orsizes, a sufficient number of cells should be characterized in order todetermine the distribution of trace orientations for the overallmicropattern with useful accuracy (e.g., where the so-measureddistribution of trace orientations exhibits an R² correlationcoefficient of at least 0.8, at least 0.9, at least 0.95, or even atleast 0.99 when compared with the actual distribution of traceorientations over an area of the actual conductor micropattern of 1millimeter by 1 millimeter, 1 centimeter by 1 centimeter, or even 1meter by 1 meter).

Once the orientations of normals (represented by the angle θ) to thetrace segments are measured, they can be binned into two micron binsthereby generating 90 bins from 0 to 180 degrees. Each bin includes aninteger representing the number of measurements that yielded anorientation within the bin's two degree angular range. This binningprocedure produces a discrete distribution of orientations. Finally, thestandard deviation of the frequency values (standard deviation ofmeasured frequency per 2 degree bin) can be calculated. For somedistributions of the normal to the trace segment, and thus thedistribution of trace orientation described herein to be considereduniform, the so calculated standard deviation is less than four. Forsome distributions of trace orientations described herein as uniform,the so calculated standard deviation is less than three. For somedistributions of trace orientations described herein as uniform, the socalculated standard deviation is less than two. For some distributionsof trace orientations therein uniform, the so calculated standarddeviation is less than one.

FIG. 7 shows a histogram of the angle θ for the multiple trace segmentsof the micropattern of FIG. 1, regular hexagon. Three distinct peaksresult at three angles, each angle being about 60 degree apart from theother peak. It should be noted that the absolute value of the angleshown on the x-axis of the histogram is arbitrary in that the threepeaks can occur at other angles, such as 40°, 100° and 160°, so long asthey are about 60° apart. The three peaks result because, with referenceto FIG. 1, the orientation angle for the normals would be the same fortraces 12 a as 12 d, 12 b as 12 e and 12 c as 12 f. For thismicropattern, the standard deviation of measured frequency per 2 degreebin was measured as 11.6, a direct indication of the highly non-uniform.

FIGS. 8, 9 and 10 show histograms of the angle θ for the pseudorandomhexagon micropattern of FIG. 2, the partially curved micropattern ofFIG. 3, and the fully curved micropattern of FIG. 4 respectively. Eachof these histograms has a broader distribution of angle θ as compared tothe histogram for the micropattern of FIG. 1, with the histogram of FIG.10 having the most uniform distribution of the four micropatterns.Furthermore, the standard deviation of these histograms is 1.6 (FIG. 8),2.6 (FIG. 9) and 1.0 (FIG. 10).

Further describing the distribution of trace segment orientations withina conductor micropattern having non-linear traces, it is within thescope of a micropattern described herein to have a uniform distributionand yet have some orientations or small ranges of orientations notrepresented in the distribution. That is, a micropattern having anabsolutely uniform distribution of trace or trace segment orientationsacross all 180° of possible orientations within a given area of themicropattern would not be removed from the scope of micropatternsdescribed herein to have a “uniform distribution” by removal of a singletrace (or trace segment) or by removal of all traces within a narrowrange of angles, for example over a 5° range of angles, or for exampleover a 2° range of angles.

With reference to the procedure described above for measuring(approximately 200 measurements) and binning (2° bins) the frequenciesof fractional trace segment orientations, the pseudorandom curvedmicropattern (FIG. 5) may have a standard deviation of measuredfrequency per 2° bin of less than 5, less than 3, less than 2, 1, oreven less than 1.

In addition to the uniformity of the distribution of trace segmentorientations, the geometry of the conductor micropatterns of the presentdisclosure can be described in terms of the radius of curvature of thetraces. In some cases, the radii of curvature for traces comprising amicropattern are less than 1 centimeter. In some cases, the radii ofcurvature for substantially all of the traces comprising the meshpattern are less than 1 centimeter. In some cases, the radii ofcurvature for traces comprising a micropattern are less than 1millimeter. In some cases, the radii of curvature for substantially allof the traces comprising the micropattern are less than 1 millimeter. Insome cases, the radii of curvature for traces comprising a mesh patternare between 50 microns and 1 millimeter. In some cases, the radii ofcurvature for substantially all of the traces comprising themicropattern are between 50 microns and 1 millimeter. In some cases, theradii of curvature for traces comprising a micropattern are between 75microns and 750 microns. In some cases, the radii of curvature forsubstantially all of the traces comprising the micropattern are between75 microns and 750 microns. In some cases, the radii of curvature fortraces comprising a mesh pattern are between 100 microns and 500microns. In some cases, the radii of curvature for substantially all ofthe traces comprising the micropattern are between 100 microns and 500microns. In some cases, the radii of curvature for traces comprising amicropattern are between 150 microns and 400 microns. In some cases, theradii of curvature for substantially all of the traces comprising themicropattern are between 150 microns and 400 microns.

Conductor Comprising a Tri-Layer Material

The tri-layer (i.e., multilayer) material conductor is comprised ofthree vacuum-deposited thin films coated in the sequence“metal-dielectric-metal”. The two metal layers differ in their opticalproperties. The first metal layer is optically opaque, thick enough toallow very low (e.g., essentially zero percent) light transmission, tobe highly reflective and not be highly absorptive. The second layer is adielectric layer, and is transparent at visible wavelengths. The thirdlayer is a semi-transparent metal layer. The tri-layer can be depositedon the surface of a substrate in either of two orientations, orsequences (i.e., with the first metal deposited first or with the secondmetal deposited first). The thin film stack, if designed properly interms of thickness and selection of metal and transparent materials, isobserved from the side having the semi-transparent metal layer toexhibit reduced reflection. The interaction of light reflected from thetop semi-transparent metal layer and the bottom opaque metal layerdetermines the spectral reflection, or observed color. In order toproduce very low, or dark reflectance, the phase difference of these tworeflections should be managed so that it is equal—and also thereflectance be as low as achievable—across the range of visiblewavelengths. This is done by choosing appropriate materials and layerthicknesses for each layer. The opaque metal layer is generally silveror aluminum, but may be another highly reflective metal with lowabsorption. The dielectric layer is a polymer layer, comprised ofacrylate materials, but may also be a visibly transparent inorganicmaterial such as silicon dioxide, and the semi-transparent metal layeris generally chromium, but may also be another metal (such as titanium)which has an optical constant (n,k) ratio near unity. If it is desiredfor the two metal layers to be electrically connected, they must have aconduction path across the transparent layer. This may occur at defectlocations in the transparent layer, the result of layer irregularitiesand faults which locally disturb layer homogeneity.

The tri-layer material can be prepared in coating chambers equipped withappropriate deposition sources in various ways; for example, sequentialand continuous, such as roll to roll coating on film or in a conveyorline coating discrete substrates. Another approach employs a batchcoating concept, one where a discrete substrate (or multiple of) isplaced into the chamber and coated, then removed and replaced with thenext batch. All three layers may be coated sequentially onto the batchin one chamber, or each batch may have one layer coated at a chamber,then moved to the next chamber for the next layer. In either approach,vacuum coating processes are best suited for coating the specifiedmaterials at the required very thin and very precise thickness levels.For the coating of metals and inorganic dielectrics, physical vapordeposition is most preferred, and electron beam deposition or sputteringare most widely used. If the dielectric (transparent) layer is organic,methods such as organic vapor deposition or plasma polymerization orliquid coating can be used.

Suitable metals for the opaque, highly reflective layer include silver,palladium, platinum, aluminum, copper, molybdenum, nickel, tin,tungsten, alloys, and combinations thereof. Suitable metals for thesemi-reflective metal layer include titanium, chromium, aluminum,nickel, copper, gold, molybdenum, platinum, rhodium, silver, tungsten,cobalt, iron, germanium, hafnium, palladium, rhenium, vanadium, silicon,selenium, tantalum, yttrium, zirconium and combinations and alloysthereof. Suitable materials for the transparent material include acrylicpolymers, SiO₂, Al₂O₃, ZrO₂, TiO₂, HfO₂, Sc₂O₃, La₂O₃, ThO₂, Y₂O₃, CeO₂,MgO, Ta₂O₅ and combinations thereof. In some embodiments, thesemi-reflective metal comprises chromium or titanium, the opaque andreflective metal comprises silver or aluminum, and the transparentmaterial comprises acrylic polymer, SiO₂, or TiO₂.

The thickness of the semi-reflective metal may be between 1 and 50nanometers, in some cases between 2 and 20 nanometers. The thickness ofthe transparent materials may be between 20 and 100 nanometers, in somecases between 40 and 80 nanometers. The thickness of the opaque highlyreflective metal may be between 50 nanometers and 10 micrometers, insome cases between 75 nanometers and 1 micrometer, and in yet othercases between 100 nanometers and 250 nanometers.

Method of Making the Conductor Micropatterns

Conductor micropatterns having the disclosed designs can be preparedusing any suitable method. Examples of methods for preparing conductormicropatterns include subtractive or additive methods. Exemplarysubtractive methods include placement of a patterned mask on a metalliccoating disposed on a substrate (e.g., a visible light transparentsubstrate), followed by selective etching (with metal being removed fromregions of the metallic coating that are not covered by the mask, andwith metal remaining in regions of the metallic coating that are coveredby the mask). Suitable masks include photoresist (patterned byphotolithography, as is known in the art), printed polymers, or printedself-assembled monolayers (for example, printed using microcontactprinting). Other exemplary subtractive methods include initial placementof a patterned lift-off mask on a substrate (e.g., a visible lighttransparent substrate), blanket coating of masked and unmasked regionswith a metallic conductor (e.g., thin film metal), and washing of thelift-off mask and any metal disposed thereon. Exemplary additiveprocesses include printing of electroless deposition catalyst on asubstrate (e.g., visible light transparent substrate) in the form of thedesired micropattern geometry, followed by patterned electroless metaldeposition (e.g., copper or nickel).

Preferred methods for generating the conductor micropatterns includemicrocontact printing. As compared with other means for reducing thereflectance of conductor patterns (coating with a carbon black-filledmaterial or partially reacting the metal to form an absorbing reactionproduct such as a sulfide), the means described herein were found to beparticularly well-suited for combination with a patterning approachbased on microcontact printing and etching, thus enabling specificmicropattern design parameters (e.g., trace width from 0.5 to 10micrometers, from 0.5 to 5 micrometers, or from 1 to 3 micrometers) andconductor thickness (e.g., the first metal layer or the second metallayer having thickness from 0.001 to 2 micrometer, from 0.05 to 1micrometer, 0.075 to 0.5 micrometer, or from 0.1 to 0.25 micrometer) tobe fabricated. The placement of carbon black-filled materials on micronscale features is impractical. The partial chemical conversion ofsub-micron thick metals (e.g., 0.075 to 0.5 micrometer, or from 0.1 to0.25 micrometer) to an absorptive reaction product is not effective forsubstantially reducing the reflectance without also substantiallyreducing the electrical conductance of the layer.

In the case of the substrate (e.g., visible light transparent)comprising nanostructured surface that is antireflective when exposed toair: a substrate is provided that includes a surface that isnanostructured and that is antireflective when exposed to air; ametallic conductor is deposited (e.g., by sputtering or by evaporation)onto the surface; a self-assembled monolayer (SAM) is printed in apattern using an elastomeric stamp; and finally the metal is etched fromdeposited metal regions not having the SAM and not etched from depositedmetal regions that include the SAM.

In the case of the tri-layer material conductor: a substrate (e.g.,visible light transparent) is provided, with a major surface; asemi-reflective metal is deposited on the substrate surface (in somecases titanium with thickness between 1 and 20 nanometers); atransparent material is deposited on the semi-reflective metal (in somecases SiO₂ with thickness between 50 and 100 nanometers); an opaquereflective metal is deposited on the transparent material (in some casesTi metallic conductor is deposited first as an adhesion promoting layerwith a thickness of from 5 angstroms to 5 nanometers, followed by silverwith a thickness of from 50 nanometers to 250 nanometers); aself-assembled monolayer (SAM) is printed in a pattern using anelastomeric stamp; and finally the silver is etched from deposited metalregions not having the SAM and not etched from deposited metal regionsthat include the SAM; in a second stage of etching, the subsequentlayers of material under the opaque, reflective metal are etched fromdeposited metal regions not having the SAM and not etched from depositedmetal regions that include the SAM.

Method of Making an Article Using Micropattern Conductors

A conductor micropattern disposed on a surface of a substrate is usefulfor making a number of different articles. Components that comprisetransparent conductive patterns include touch sensor panels for touchdisplays. Some touch sensor panels for touch displays, for example sometouch sensor panels that are suitable for combination with electronicsthat utilize mutual capacitance mode detection and that may includemulti-touch resolution capability, include two or more conductorpatterns that are overlaid. Two or more conductor patterns that areoverlaid can be generated by laminating two substrates together with aclear adhesive, each substrate having disposed on one its major surfacesa conductor micropattern according to the present disclosure. Suchlaminated articles can be visible light transparent when the substratesare transparent and when the conductor micropattern have high open areafraction. Examples of suitable substrates for forming laminatedconstructions include the polymeric film substrates listed above.

Examples of suitable adhesive materials for forming laminatedconstructions are optically clear adhesive that exhibit an opticaltransmission of at least about 90%, or even higher, and a haze value ofbelow about 5% or even lower. Optical transmission and haze can bemeasured by disposing it between a 25 micrometer Melinex® polyester film454 (from DuPont Company, Wilmington, Del.) and a 75×50 millimeter plainmicro slide (a glass slide from Dow Corning, Midland, Mich.) using aModel 9970 BYK Gardner TCS Plus Spectrophotometer (from BYK Gardner,Columbia, Md.). Suitable optically clear adhesive may have antistaticproperties, is compatible with metal-based conductors, may be able to bereleased from the glass substrate by stretching the adhesive describedin Illustrative optically adhesive include those described in PCTInternational Publication No. WO 2008/128073 relating to antistaticoptically pressure sensitive adhesive, U.S. Patent ApplicationPublication Nos. US 2009-030084 A1 relating to stretch releasingoptically clear pressure sensitive adhesive, US 2010-0028564 A1 relatingto antistatic optical constructions having optically transmissiveadhesive, PCT International Publication Nos. WO 2009/114683 relating tooptically clear stretch release adhesive tape, WO 2010/019528 relatingto adhesives compatible with corrosion sensitive layers, and WO2010/078346 stretch release adhesive tape. In one embodiment, theoptically clear adhesive has a thickness of about 5 μm or less.

A substrate having the conductor micropattern disposed thereon, oralternatively a laminate comprising two or more substrates having theconductor micropatterns disposed thereon, can be further laminated to adisplay, for example a liquid crystal display (LCD), an organiclight-emitting diode (OLED) display, a plasma display panel (PDP), anelectrophoretic display (EP), or an electrowetting display. Such asubstrate or laminate can be laminated to the display using thereferenced adhesive materials. A substrate having the conductormicropattern disposed thereon, or alternatively a laminate comprisingtwo or more substrates having the conductor micropatterns disposedthereon, can be further laminated to another material, for example arigid support such as a thick (e.g., 1 millimeter) polymer sheet orglass sheet. Examples of rigid supports include the lenses of mobilehandheld devices such as mobile phones or smart phones.

In some embodiments, a conductor micropattern as described herein isdisposed on more than one side of a substrate, for example on each majorsurface of a flat substrate that may be flexible or rigid, as alreadydescribed. For applications that require two conductor micropatternsthat are nominally parallel in orientation and spaced apart in thedirection normal to the micropatterns, it may be advantageous for thetwo micropatterns to be disposed on each side of the same flatsubstrate, for example on each side of a polymer film.

FIG. 11 shows an exemplary first patterned substrate 700 schematically(not to scale) having a plurality of first continuous regions 702alternating between a plurality of first discontinuous regions 704 on afirst side of the substrate, which is the side that contains the etchedand patterned tri-layer (i.e., multilayer) conductor. The tri-layerconductor can be oriented with its semi-transparent metal layerproximate to the substrate, followed by its transparent dielectriclayer, followed by its highly reflective optically opaque metal layer.The first patterned substrate actually has 11 first continuous regions702. The first continuous regions 702 has width of approximately 2.2millimeters, pitch of approximately 4.95 millimeters, and length ofapproximately 95 millimeters. The substrate has an opposing second sidethat was substantially bare PET film. Each of the first regions 702 hasa corresponding 40 micron wide conductive trace 706 disposed at one end,for making electrical contact to each first continuous region 702. Themesh designs for the first patterned substrate can be pseudorandom inshape and size, including curvature for the conductive traces making upthe meshes, as noted above (in contrast to the hexagonal mesh designsdepicted in FIGS. 11a and 11b ).

Formation of a Transparent Sensor Element Second Patterned Substrate

An exemplary second patterned substrate can be made as the firstpatterned substrate using a second visible light substrate to produce asecond film with patterned tri-layer (i.e., multilayer) conductor. Thetri-layer conductor can be oriented with its semi-transparent metallayer proximate to the substrate, followed by its transparent dielectriclayer, followed by its highly reflective optically opaque metal layer. Asecond stamp can be produced having second continuous mesh patternregions interposed between second discontinuous mesh pattern region.

FIG. 12 shows the second patterned substrate 720 schematically (not toscale) having a plurality of second continuous regions 722 alternatingbetween a plurality of second discontinuous regions 724 on a first sideof the second substrate, which is the side that contains the etched andpatterned silver metallization. The second patterned substrate actuallyhas 19 first continuous regions 722. The second continuous regions 722has width of approximately 4.48 millimeters, pitch of approximately 4.93millimeters, and length of approximately 55 millimeters. Each of thesecond continuous regions 722 has a corresponding 40 micron wide secondconductive trace 726 disposed at one end, for making electrical contactto each second continuous region 722. The mesh designs for the firstpatterned substrate can be pseudorandom in shape and size, includingcurvature for the conductive traces making up the meshes, as noted above(in contrast to the hexagonal mesh designs depicted in FIGS. 12a and 12b).

Formation of a Projected Capacitive Touch Screen Sensor Element

The first and second patterned substrates made above can be used toproduce a two-layer projected capacitive touch screen transparent sensorelement as follows. The first and second patterned substrates wereadhered together using Optically Clear Laminating Adhesive 8271 from 3MCompany, St. Paul, Minn. to yield a multilayer construction. A handheldroller was used to laminate the two patterned substrates with theregions of the first and second conductive trace regions 706 and 726being adhesive free. The multilayer construction was laminated to a 0.7mm thick float glass using Optically Clear Laminating Adhesive 8146-3such that the first side of the first substrate was proximate to thefloat glass. The adhesive free first and second conductive trace regions706 and 726 allowed electrical connection to be made to the first andsecond patterned substrates 700 and 720.

FIG. 13 shows schematically (not to scale) a top plan view of amultilayer touch screen sensor element 740 where the first and secondpatterned substrate have been overlaid (as would result from laminatingthe first and second patterned substrates). Region 730 represents theoverlap of the first and second continuous regions. Region 732represents the overlap of the first continuous region and the seconddiscontinuous region. Region 734 represents the overlap of the secondcontinuous region and the first discontinuous region. And, region 736represents the overlap between the first and second discontinuousregions. While there was a plurality of these overlap regions, for easeof illustration, only one region of each has been depicted in thefigure.

Additional Components of the Touch Sensing System

The integrated circuits that can be used to make mutual capacitancemeasurements of the transparent sensor element are the CY3290-TMA300TrueTouch™ Dev Kit with revision reference Rev *D, containing an I2C toUSB converter bridge and microcontroller TMA350 (commercially availablefrom Cypress Semiconductor, San Jose, Calif.). The TMA350 can beconfigured for the transparent sensor element, as is known in the art.The configuration can vary from touch screen to touch screen, dependingon design. In this case, the system can drive 19 different bars andmeasure 11 different bars. The configuration of the TMA350 can includeselection of the number of channels to convert, how accurately orquickly to take measurements, the noise and touch thresholds, anydigital filtering to be applied and various other settings particular tothe CY3290-TMA300. While the measurement from above was running, themicrocontroller was also sending the data to a computer with monitor viathe TrueTouch™ Bridge, which converts I2C from the TMA350 to USB for thecomputer interface. This USB interface allows the Cypress TrueTouch™software to render data from the TMA350 and see how the values werechanging between a touch and no touch.

Results of Testing of the Touch Sensing System

The transparent sensor element can be connected to the touch sensordrive device. When a finger touch is made to the glass surface, thecomputer monitor can render the position of touch that occurs within thetouch sensing region in the form of a color change (black to green) inthe corresponding location of the monitor and displayed the location inan adjacent display to simulate the result of the touch screen system.When two, three, and four finger touches are made simultaneously to theglass surface, the computer monitor can render the positions of touchesthat occur within the touch sensing region in the form of a color change(black to green) in the corresponding locations of the monitor anddisplayed the location in a touch screen simulation display.

Applications

In some embodiments, the articles described herein comprise a conductormicropattern comprising non-linear traces defining an open micropatternof a cell geometry disposed on or in a visible light transparentsubstrate. In some such embodiments, the conductor micropattern forms atleast a portion of an EMI shield. In some such embodiments, theconductor micropattern forms at least a portion of an antenna. In somesuch embodiments, the conductor micropattern forms at least a portion ofa touch sensor (for example a touch screen sensor). In some suchembodiments, the conductor micropattern forms at least a portion of adisplay electrode, for example a counterelectrode, for example acounterelectrode in an electrophoretic display.

In some embodiments, the articles described herein comprise a firstconductor micropattern comprising non-linear traces defining a firstopen micropattern of a cell geometry disposed on or in a visible lighttransparent substrate and a second conductor micropattern comprisingnon-linear traces defining a second open micropattern of a cell geometryelectrically isolated from the first conductor micropattern. The secondconductor micropattern may be disposed on the same substrate as thefirst conductor micropattern, or it may be disposed on anothersubstrate. The second conductor micropattern overlays the firstconductor micropattern.

In some embodiments, both conductor micropatterns form at least aportion of a touch sensor, for example a touch screen sensor.

In some embodiment, both conductor micropatterns form at least a portionof an electrophoretic display.

Alternatively, in another embodiment, one of the conductor micropatternsforms at least a portion of a touch sensor, for example a touch screensensor, and the other conductor micropattern may function as an antennafor wireless communication.

In yet another embodiment, one of the conductor micropatterns forms atleast a portion of a touch sensor, for example a touch screen sensor,and the other conductor micropattern may function as an electromagneticinterference (EMI) shield.

In yet another embodiment, one of the conductor micropatterns forms atleast a portion of an antenna for wireless communication and the otherconductive micropattern may function as an electromagnetic interference(EMI) shield.

EXAMPLES Substrates

Two different substrates were used in this example section.

A first substrate was a visible light transparent substrate ofpolyethylene terephthalate (“PET”) having a thickness of approximately125 micrometers, commercially available as product number ST504 fromE.I. du Pont de Nemours, Wilmington, Del. was used.

A second substrate was a structured triacetate film (“Structured TAC”)prepared according to the disclosure of WO 2010/07871 A1. The startingsubstrate was a cellulose triacetate film having a thickness of 75micrometers (commercially available from Island Pyrochemical IndustriesCorp., New York, N.Y.). This TAC film was thus modified to contain ananostructure on a first surface of the substrate. The nanostructuredsurface exhibited a reflectance of 0.1-0.2%. The nanostructured surfaceexhibited a transmitted haze of 0.2-0.4%. The nanostructured surfacecomprised nanofeatures that were 100 to 250 nanometers in height. Theheight to width ratio (anisotropy) of the nanofeatures was greater thanone.

Conductor

Onto the PET substrate or the Structured TAC substrate was deposited thefollowing conductive coatings:

(1) a “sputtered silver” film, which is a multilayer construction of 5angstrom thick of titanium disposed directly on the substrate followedby 100 nanometers thick of silver, both deposited using known vacuumsputtering methods, or

(2) an “evaporated silver” film, which is a multilayer construction of 5angstrom thick of titanium disposed directly on the substrate followed100 nanometer thick of silver, both deposited using known electron-beamevaporation methods; or

(3) an “evaporated multilayer” conductor, which is a multilayerconstruction of 15.5 nanometer thick first layer of titanium disposeddirectly on the substrate followed by 70 nanometer thick layer ofsilicon dioxide, followed by 2.2 nanometer thick second layer oftitanium, followed by 90 nanometer of silver, all layers deposited usingknown electron beam evaporation method.

After deposition of the conductive coating, the substrate has a coatedside containing the conductive coating and an opposite side, i.e., sidewith no conductive coating.

The conductive coating used for each geometry for examples herein waspatterned by printing octadecylthiol self-assembled monolayer mask onits surface, followed by wet chemical etching, as described in U.S.Patent Application Publication No. US 2009/0218310. In the wet chemicaletching step of the process for the evaporated multilayer conductor, alllayers of the conductor (i.e., the first titanium layer, the silicondioxide, the second titanium layer and the silver layer) were etchedexcept in the area where the micropattern was to remain to form thetraces.

Characterization of Substrate

The average percent reflection (% R) was used to measure both majorsurfaces (coated and bare sides) of the substrate (whether PET orStructured TAC) using a BYK Gardner color guide sphere.

One sample of each film was prepared by applying Yamato Black Vinyl Tape#200-38 (commercially available from Yamato International Corporation,Woodhaven, Mich.) to the opposite side of the measuring surface using aroller to minimize trapping air bubbles. To measure the surface total %reflection (specular and diffuse), the non-taped side of the sample wasplaced against an aperture of BYK Gardiner Color-Guide Sphere. The %reflection was measured at 10° incident angle for the wavelength rangeof 400 to 700 nm. Note that when reflectivity is measured from the bareside (i.e., opposite the conductor-coated side), the measuredreflectivity includes reflection from the interface between thesubstrate film and air. The % R for the substrates with the conductorsare shown in Table 1 below.

TABLE 1 Reflectance measurements Reflectance (%), Reflectance (%),Substrate Conductive measured from measured from Type Coating Typecoated side bare side PET Sputtered Ag 93.71 88.68 PET Evaporated Ag92.65 88.89 PET Evaporated Multilayer 93.56 20.64 Structured SputteredAg 79.44 7.52 TAC

Comparative Example C1

This example was made by using PET substrate and Sputtered Ag conductorusing a regular hexagon conductor micropattern. The trace widths wereapproximately 2 micrometers. The diameter of the hexagonal cells (fromface to parallel face) was approximately 200 micrometers. The open areafraction was approximately 98%.

Comparative Example C2

This example was made by using PET substrate and Sputtered Ag conductorusing a regular hexagon conductor micropattern. The trace widths wereapproximately 2 micrometers. The open area fraction was approximately98%.

Examples 3 Through 6

These examples were made by using the Structured TAC substrate andSputtered Silver conductor with a regular hexagonal micropattern (Ex.3), a pseudorandom hexagonal micropattern (Ex. 4), a partially curvedhexagonal micropattern (Ex. 5) and a fully curved hexagonal micropattern(Ex. 6). In all cases, the trace widths were approximately 2 micrometersand the open area fractions were approximately 98%.

Example 7

This example can be made using the PET substrate and evaporatedmultilayer conductor. The pattern design is a regular hexagonal meshwith cell diameter of approximately 200 micrometers and trace width ofapproximately 2 micrometers. The open area fraction is approximately98%. Following the patterning of the silver layer of the tri-layermaterial conductor, by microcontact printing followed by wet chemicaletching (as referenced above), the subsequent layers of the EvaporatedMultilayer conductor can be etched by wet chemical etching with asolution of 10:1 buffered oxide etch solution (385 mL; 10 parts 40% NH₄Fsolution to 1 part 49% HF solution by volume). The multilayer film canbe placed in the etch bath, on the surface of the solution with thepatterned side facing down, in a plastic pan. The film should be removedfrom the etch bath after 62 seconds, rinsed immediately with a stream ofDI water, and dried with an air gun.

Examples 8 Through 10

These examples were made by using the PET substrate and evaporatedmultilayer conductor with a pseudorandom hexagonal micropattern (Ex. 8),a partially curved hexagonal micropattern (Ex. 9) and a fully curvedhexagonal micropattern (Ex. 10). In the cases of Examples 8-10, thetrace widths were approximately 2 micrometers and the open areafractions were approximately 98%. Following the patterning of the silverlayer of the tri-layer material conductor, by microcontact printingfollowed by wet chemical etching (as referenced above), the subsequentlayers of the evaporated multilayer conductor were etched by wetchemical etching with a solution of 10:1 buffered oxide etch solution(385 mL; 10 parts 40% NH₄F solution to 1 part 49% HF solution byvolume). The multilayer film was placed in the etch bath, on the surfaceof the solution with the patterned side facing down, in a plastic pan.The film was removed from the etch bath after 62 seconds, rinsedimmediately with a stream of DI water, and dried with an air gun.

Example 11

This example can be made using the Structured TAC substrate andSputtered Silver conductor with a pseudorandom curved micropattern.

Example 12

This example can be made using the PET substrate and evaporatedmultilayer conductor with a pseudorandom curved micropattern.

TABLE 2 Summary of the examples Example Substrate Conductive CoatingPattern Design Number Type Type Type C1 PET Sputtered Ag regular hexagonC2 PET Sputtered Ag pseudorandom hexagon 3 Structured Sputtered Agregular hexagon TAC 4 Structured Sputtered Ag pseudorandom hexagon TAC 5Structured Sputtered Ag partially curved hexagon TAC 6 StructuredSputtered Ag fully curved hexagon TAC 7 PET Evaporated Multilayerregular hexagon 8 PET Evaporated Multilayer pseudorandom hexagon 9 PETEvaporated Multilayer partially curved hexagon 10 PET EvaporatedMultilayer fully curved hexagon 11 Structured Sputtered Ag pseudorandomcurved TAC 12 PET Evaporated Multilayer pseudorandom curved

Characterization of the Articles

Laminated articles having one or more conductor micropatterns wereevaluated for the conspicuity of their micropatterns under sunlightillumination. The evaluation included visual inspection withoutmagnification (unaided eye). The samples were further imaged using adigital camera (iPhone 3GS, Apple Computer Corp, Cupertino, Calif.). Thesunlight illumination upon each sample was first attenuated by passagethrough a typical commercial architectural double-pane insulated glassunit window having a semi-reflective energy-management film applied, inorder to reduce the intensity of light reaching the eye or the camera toa more suitable level for viewing or recording. A number of visualeffects contributed to the conspicuity of the various micropatterns. Afirst such visual effect category is described herein as “starburst,”which takes the form of a bright reflective pattern in the shape of amulti-pointed star when illuminated with bright (non-diffuse) sunlight.A regular hexagonal mesh can give rise to a six-pointed starburst. Aregular square mesh can give rise to a four-pointed starburst. A secondvisual effect category is described herein as “rainbow,” which takes theform of a band of reflection exhibiting a spectrum of colors along theband when illuminated with bright (non-diffuse) sunlight. A third visualeffect category is described herein as “colored halo,” which takes theform of diffuse pink and green halos that surround the point of directspecular reflection when illuminated with bright (non-diffuse) sunlight.A fourth visual effect category is described herein as “sparkle,” whichtakes the form of bright points of light across the micropattern whenilluminated with bright (non-diffuse) sunlight.

TABLE 3 Results of visual inspection for conductor micropattern examplesExample Starburst Rainbow Colored Halo Sparkle Number Score Score ScoreScore C1 ⊗ ⊗ ⊕ ⊕ C2 ⊗ ⊕ ⊕ ⊗ 3 ⊕ ⊕ ⊕ ⊕ 4 ⊕ ⊕ ⊕ ⊕ 5 ⊕ ⊕ ⊕ ⊕ 6 ⊕ ⊕ ⊕ ⊕ 7N/A N/A N/A N/A 8 ⊕ ⊕ ⊕ ⊕ 9 ⊕ ⊕ ⊕ ⊕ 10  ⊕ ⊕ ⊕ ⊕

The data in TABLE 3 in terms of score for starburst, rainbow, sparkleand colored halo are reported in terms of an acceptable visualappearance score, represented by and an unacceptable visual appearancescore ⊗. In determining the score, an acceptable score did not imply atotal absence of the visual artifact (whether it is a starburst,rainbow, halo or sparkle) but, if present, the level of the artifact isat a level where it may be acceptable to a user (at least, moreacceptable than for examples scored with ⊗). For Examples 3-6, ascompared with C1 and C2, an improvement in appearance (less conspicuousfeatures of the micropattern) was achieved for evaluation from eitherdirection, relative to the micropattern (i.e., from the substrate film(nanostructure surface) side or from the side opposite the substratefilm). The improvement (reduced conspicuity) was greater for evaluation(viewing) from the substrate film side.

Results of electrical and transmitted optical measurements for laminatedconductor micropattern examples are reported in Table 4. Entriesassigned to TAC and PET were derived from measurements made for eachsubstrate type, laminated to glass as described above (baseline data).The light transmittance (% T), clarity (% C), and transmitted haze (% H)were measured using a Haze-Gard Plus (BYK-Gardner, Columbia, Md.).

TABLE 4 % T % H % C % T % H % C Sheet Example Film Film Film Glass GlassGlass Resist Number Side Side Side Side Side Side (ohm/sq) C1 90.2 2.1799.5 90.1 2.08 99.6 30 C2 90.1 2.59 99.5 90.1 2.64 99.5 28 3 90.8 2.2099.4 90.5 2.25 99.4 59 4 90.6 2.68 99.5 90.3 2.78 99.5 100 5 91.1 1.8999.5 90.9 1.82 99.5 42 6 91.2 2.09 99.5 91.1 2.04 99.5 40 7 N/A N/A N/AN/A N/A N/A N/A 8 87.9 2.05 99.3 87.8 1.92 99.4 23 9 88.4 1.86 99.3 88.21.85 99.4 25 10  88.6 2.00 99.5 88.9 2.04 99.5 40 TAC 93.9 0.72 100 93.90.69 100 N/A PET 91.8 0.60 100 91.8 0.60 100 N/A

Results of reflectance measurements for laminated conductor micropatternexamples are reported in Table 5. Entries assigned to TAC and PET werederived from measurements made for each substrate type, laminated toglass as described above (baseline data). As shown in Table 5, themicropattern contributes less reflectance when disposed on thenanostructured substrate surface (that is antireflective when exposed toair), as compare with identical micropatterns disposed on standardsubstrate film (PET), when the former is when viewed and measured fromthe substrate side of the micropattern.

TABLE 5 % Reflectance % Reflectance % R Contribution Contribution fromExample Film from Micropattern % R Micropattern (Glass Number Side (FilmSide) Glass Side Side) C1 10.1 1.0 10.0 0.9 C2 10.2 1.0 10.2 1.1 3 7.20.2 8.3 1.3 4 7.3 0.3 8.1 1.1 5 7.5 0.5 8.7 1.7 6 7.3 0.3 8.4 1.3 7 N/AN/A N/A N/A 8 9.8 0.6 11.8 2.7 9 10.0 0.8 11.4 2.3 10  9.8 0.6 11.1 2.0TAC 7.0 N/A 7.0 N/A PET 9.2 N/A 9.1 N/A

What is claimed is:
 1. An article comprising: a conductor micropatterndisposed on a major surface of a substrate, the micropattern comprisinga plurality of traces defining a plurality of mesh cells not lying on arepeating array defined by unit cells comprising four or fewer positionswith each position corresponding to a mesh cell, each trace in theplurality of traces having a radius of curvature less than 1 centimeter.2. The article of claim 1, wherein a number of traces that defines amesh cell in the plurality of mesh cells varies over the micropattern.3. The article of claim 2, wherein the number of traces that defines amesh cell in the plurality of mesh cells varies from 4 to
 8. 4. Thearticle of claim 1, wherein each trace in the plurality of traces has aradius of curvature between 50 microns and 1 millimeter.
 5. The articleof claim 1, wherein each trace in the plurality of traces has a radiusof curvature between 75 microns and 750 microns.
 6. The article of claim1, wherein each trace in the plurality of traces has a radius ofcurvature between 150 microns and 400 microns.
 7. The article of claim1, wherein each trace comprises a semi-transparent metal, an opaquemetal, and a transparent material disposed therebetween.
 8. The articleof claim 7, wherein the semi-transparent metal has a thickness between 1nanometer and 50 nanometers and the opaque metal has a thickness between75 nanometers and 1 micrometer.
 9. The article of claim 8, wherein thethickness of the semi-transparent metal is between 2 nanometers and 20nanometers.
 10. The article of claim 8, wherein the thickness of theopaque metal is between 100 nanometers and 250 nanometers.
 11. Thearticle of claim 7, wherein the transparent material has a thicknessbetween 20 nanometers and 100 nanometers.
 12. The article of claim 7,wherein the semi-transparent metal comprises chromium or titanium. 13.The article of claim 7, wherein the opaque metal comprises silver oraluminum.
 14. The article of claim 7, wherein the semi-transparent metaland the opaque metal are electrically connected to one another throughconduction paths across the transparent material.
 15. The article ofclaim 1, wherein the plurality of traces has a uniform distribution oftrace orientation for the micropattern.
 16. The article of claim 15,wherein the uniform distribution of trace orientation for themicropattern has a standard deviation of measured frequency per twodegree bin of less than four.
 17. The article of claim 15, wherein theuniform distribution of trace orientation for the micropattern has astandard deviation of measured frequency per two degree bin of less thantwo.
 18. The article of claim 1, wherein each mesh cell in the pluralityof mesh cells has an open area, the open area varying over themicropattern.
 19. The article of claim 1, wherein each trace in theplurality of traces has a width in a range of 0.5 to 4 micrometers. 20.The article of claim 1, wherein each trace in the plurality of traceshas a width in a range of 0.5 to 3 micrometers.